Regulation of polyphase commutating motors



Nov. 24, 1925. 1,562,786 J. FERRET REGULATION OF POLYPHASE COMMUTA'I'INGMOTORS Filed March 20, 1922 2 Sheets-Sheet 1 Nov. 24, 1925- Filed March20, 1922 2 Sheets-Sheet 2 I), \1 m relented Iver.

UNITE PATENT car es- JOSEPH FERRET, OF PARIS. Fl-RANGE, AfiSIGIQ'OE/ T0FOBGES & ATELIERS DE CON- STRUCTIONS ELECTRIQUES DE JEUIEGHT, 03E PARIS,FRANCE.

Application filed March 20, 1922.

To all iii/zone it may concern Be it known that I, Josnri-r Pannier, acitizen otthe Republic of lirance residing at Paris, in the Republic 01France have invented certain new and useful Improvements in theRegulation of Polyphase Commutating Motors, of which the following aspecification.

Polyphase comn'lutator meters are not adapted in their simple form forthe operation of rolling mills because this application requires arelatively slight slip (l0-15/() and one which is practically constantat all speeds.

In order to obtain this result with a view to the said'application. ithas already been suggested to connect in shunt across the retor of theseries motor a circuit comprising an inductance and a voltage ofsuitable value and. phase with a "View to ensuring the excitation oi?the machine by its rotor equally well when runn ng under load or runninglight; butin the ordinary :tornrthe regulation of the voltage and theinductance present difiiculties.

The system which terms the object oi this invention comprisesarrangements which carry out these conditions in practice by asimplified operation which may also be combined with automaticarrangements onabling any running characteristic to be obtained whilstpreventing wrong OPGlatlOll.

According to this invention the voltage of the shunt circuit is obtainedfrom a double induction regulator inwhich the primary coils are fed bythe stator of the connnntator motor instead oi? being ted directly fromthe net-work.

The inductance may be regulated by hand or by means o'l automaticdevices with a view to obtaining any characteristic or for preventingwrong operations.

The brush position 01'? the motor may rc main fixed so-that theautomatic or hand regulation may be applied solely to that of theregulator and the inductance.

The invention? is more particularly de scribed with reference to theaccompanying drawing in which i Fig. 1 shows diagrammatically thearrangement according to this invention.

Fig. 2 shows a method of carrying the same.

out

REGULATION OF POLYEIIASIJ COIKM'UTATZNG IIIOTORS.

Serial No. 545,26'72 Fig. 3 is a diagram showing the relations of the E.ill. Ffs of the regulator.

M is a three phase series commutator inotor fed from the terminals X; Ris a. double induction regulator the primary windings of which (stators)22 7 mounted in parallel are fed by the stator of the motor M; thesecondary windings (rotors) 1' T of this regulator It and the ad ustableinductance S are mounted in. series andthis circuit is connected inshunt across therotor of the motor M.

The regulation of the induction regulator the angle at adjustment of thebrushes. It

is well. known that in a double regulator the resultant voltage of therotors can be regulated in order to give any predetermined anglerelatively to the common voltage of the stators by suitable displacementoil? one rotor relatively to the other. This displacement beingefl'ected once and for all the simultaneous adjustment to the two r0tors will modify the value and not the phase of the resultant voltage.

ln Fig. 3 c and 9' 7 and T are the l). M. F.s induced in the rotorscorresponding to two diiterent positions; R and R are t-l'ieresultantM.- F.s in the two cases, the two elements of the regulator beingconsidered identical. The same result will be obtained it the statorfields rotate in the same direction while therotors are turned.

in parallel with the statorof the motor M the result is that for aconstant position of the brushes of the latter, the. potentialof therotor of the said m0tor M- and'that of the primariesp 501 theregulator Rare constantly mutually displaced by a constant angle Whatever may bethe speed of the 1notor and the controlling position of the regulator.

It is therefore sufficient to regulate the brush position of the motorand the rela tive osition of the rotors and stators of the regu ator toobtain any suitable phase displacement of the voltages, and thisdisplacement will be maintained whatever the speed and Whatever themagnitude of the voltages.

For example the terminal voltages of the regulator R and motor M may bemaintained in phase. In this case as the reactance of the shunt circuitis generally much more important than its resistance, the currentof thiscircuit will be constantly out of phase with the electromotive force ofthe rotor of the motor M by 90 that is to say that it will be constantlymagnetizing. In particular when running light the magnetizing currentwill be entirely furnished by the rotor of the motor M and the powerfactor may be equal to unity.

For each load there corresponds an adjustment of the regulator whereinits E. M. F. is equal to that of the commutator motor so that when underload at a given speed the commutator voltage will be equal and directlyopposed to that of: the regulator R whereby the current of the shuntcircuit is neutralized and the motor works at one of its speeds as aseries motor. Its power factor is thus that of the series motor havingthe same speed and brush position.

Thus the full load speed may be regulated to any suitable value by theregulator R, and the power factor is automatically main tained inproximity to unity equally well whether the machine is under load. orrun ning light.

In the above it is assumed that the resistance of the shunt circuitrelatively to its reactance is negligible. When this resistance isrelatively large it might be compen sated by employing a doubleregulator, the two rotors 1' 73, of which are arranged with having aslightly difierent number of turns.

The difference in speed between running under series load and runninglight is practically constant because it depends substantially on theinductance of the shunt circuit.

The relation between the speed and the inductance of the shunt circuitmay be obtained as follows: It

I is current in the stator.

I is current in the shunt circuit at the terminals of the rotor.

E, is E. M. F. at the terminals of the stator.

E is E. M. F. at the termials of the rotor.

E is E. M. F. at the terminals of the secondary of the double regulator.

L is inductance of the rotor.

L, is inductance of the shunt circuit.

9., is the slip at no load as a percentage of the synchronous speed.

g is the slip under load as a percentage of the synchronous speed.

L is the inductance of the stator.

When running light the current in the stator is nil so that the E. M. F.at its terminals is equal to E K oMI I being at this moment the strengthof the current circulating in the circuit formed by the rotor, doubleregulator and the adjustable inductance, M the co-elticient of mutualinductance between the stator and the rotor and K a co-etlicient whichis a function of the angle of adjustment of the brushes E g oL I whenceE KM but E is also equal to coL I -t-E so that wL I -l-E =E E KM L I KME KM L, e; 1T d awn; LTI

lVhen running under load there is a moment when the E. M. F. at theterminals of the rotor is equal to the E. M. F. at the terminals of thedouble regulator, the latter having been previously adjusted "for thisobject and at this instant a current in the shunt circuit is neutralizedand the motor operates as a simple series motor with a slip g Thereforethe difference of the slip when runmng light and under load 1s given byalso be etlected either in order to limit to a given value the powerabsorbed or to hunt the current in 1ts own circuit or for any otherpurpose and for these different cases mechanisms such as servo-motorsand the like may be employed.

In particular as it is preferable that the starting should be effectedas a series motor it will thus be necessary that the inductance S shouldtake automatically, during this operation, a high value so as to limitits own current.

This result may be obtained for example as shown in Fig. 2 by the use ofan inductance having a variable air gap a, the movable part 1 is mountedto move against springs 2. If the value of the current in the windings 3of the inductance S increases beyond a certain value, the air gaps adiminish compressing the springs 2 and thus this automatic variation ofthe inductance will limit its current.

The air gap a may be given any desired adjustment by means of a handwheel 4 moving the movable part 1 of the core through worm or the likegearing 5.

This automatic arrangement has the advantage of avoiding breaking thefeed circuit by the circuit breaker in the case of an error inoperation.

I declare that what I claim is 1. A controlling system for polyphasecommutator motors comprising in combination a polyphase commutator motorhaving stator and rotor windings connected in se ries, an inductionregulator having double primary and secondary windings, electricalconnecting means between said stator and said primary windings,electrical connecting means between said secondary winding and saidrotor winding and means to vary the phase displacement of the voltagesof said motor and said regulator.

2. A controlling system for polyphase commutator motors comprising incombination a polyphase commutator motor, having stator and rotorwindings connected in series, an induction regulator having doubleprimary and secondary windings, connecting means between said stator andsaid primary windings, connecting means between said secondary windingand said rotor and an inductance in series with said secondary windingsand means to vary the phase displacement of the voltages of said motorand said regulator.

3. A controlling system for polyphase commutator motors comprising apolyphase commutator motor having stator and rotor windings, a doubleinduction regulator, primary windings in said regulator shunted acrosssaid stator, secondary windings in said regulator in shunt across saidrotor and a variable inductance in series with said secondary windings.

l. A controlling system for polyphase commutator motors comprising apolyphase commutator motor having stator and rotor windings, a doubleinduction regulator, primary windings in said regulator shunted acrosssaid stator, secondary windings in said regulator in shunt across saidrotor, a variable inductance in series with said secondary windings andmeans for automatic adjustment of said inductance according to thecurrent flowing there-through.

In witness whereof, I have hereunto signed my name this 28 day ofFebruary JOSEPH FERRET.

